1. Field of the Invention
The present invention relates to facsimile apparatuses, and more particularly, to a coding system for use in bandwidth compression of a facsimile signal.
2. Description of the Related Art
Various coding systems have been conventionally proposed for bandwidth compression of a facsimile signal, among which an MH (Modified Huffman) system as a standardized one-dimensional coding and an MR (Modified READ) system as a standardized two-dimensional coding are recommended by CCITT.
In the MH system, for example, image data of a line (line data) of a white pixel run or a black pixel run with L=64n+Lr (n: integer) is represented by a combination of terminating codes comprised of 64 separately determined codewords, and make-up codes determined corresponding to n (1, 2, 3 . . . ).
A facsimile apparatus is known which is structured to be capable of sending and receiving, in addition to usual black and white images (monochrome images), color images (mixed color images) such as plural color images, for example, two-color image of black and red as of a sealed document or full-color images.
A conventional facsimile apparatus applicable to color images separates colors of image data of one line, codes line data of each color and arranges and transmits the obtained coded data of each color in time sequence, wherein bandwidth compression of image data is executed under a system which is unique to a manufacturer and different from the above-described standardized coding system.
In a case of color image transmission, a conventional facsimile apparatus applies an NSF signal (nonstandard function discrimination signal) to escape from a standard mode to a special mode. Therefore, communication is not possible with most facsimile apparatuses not provided with such a special mode.
Memory transmission is also widely used in which image of an original is read prior to calling and stored as coded data in a memory in advance and the code data is read from the memory after the calling and transmitted to a destination side (called party). Since it is not possible in the memory transmission to detect whether a facsimile apparatus on a transmission destination side is provided with a special mode or not at the time of reading image of an original, if image data transmission is found to be impossible after starting transmission, the transmission is stopped to abandon the coded data stored in the memory and the original image is read again in a normal mode, which is time consuming.
An object of the present invention is to enable coding involving no useless operation in transmission under a color image data coding system.
Another object of the present invention is to achieve normal transmission under a color image data coding system irrespective of a destination facsimile apparatus""s capability of receiving color image.
In order to achieve the above-described objects, a coding system of the present invention relates to a color image data coding and includes the steps of coding image data by replacing the image data by codewords representing a white or black run-length, representing color information by combing specific codewords among the codewords and by combining the coded image data and the color information to represent image data including color image by codewords only.
Under the coding system as structured above, image data including color image is represented only by codewords, so that quick image data transmission is possible irrespective of reception function of a destination apparatus.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.